（IOS）根據bundle中的檔名讀取圖片

+ (UIImage*)imageWithFileName:(NSString*)name {

    NSString*extension =@"png";

    NSArray*components = [namecomponentsSeparatedByString:@"."];

    if([componentscount] >=2) {

        NSUIntegerlastIndex = components.count-1;

        extension = [componentsobjectAtIndex:lastIndex];

        name = [namesubstringToIndex:(name.length-(extension.length+1))];

    }

    // 如果為Retina螢幕且存在對應圖片，則返回Retina圖片，否則查詢普通圖片

    if([UIScreenmainScreen].scale==2.0) {

        name = [namestringByAppendingString:@"@2x"];

        NSString*path = [[NSBundlemainBundle]pathForResource:nameofType:extension];

        if(path !=nil) {

            return [UIImage imageWithContentsOfFile:path];

        }

    }

    if([UIScreenmainScreen].scale==3.0) {

        name = [namestringByAppendingString:@"@3x"];

        NSString*path = [[NSBundlemainBundle]pathForResource:nameofType:extension];

        if(path !=nil) {

            return [UIImage imageWithContentsOfFile:path];

        }

    }

    NSString*path = [[NSBundlemainBundle]pathForResource:nameofType:extension];

    if(path) {

        return [UIImage imageWithContentsOfFile:path];

    }

    return nil;

}